Although federal law requires certifying agencies to test for pesticides and toxins, USDA regulations do not require testing for genetically engineered material, the audit said.

Genetic engineering is prohibited from organic production, but the presence of transgenic material in an organic crop wouldn't be considered a violation of organic rules if the farmer tried to prevent such contamination, the audit said.

Though certifying agencies rely on certificates to confirm that feed is organic, it's unlikely they would actually test such crops, the audit said.

Officials from USDA's National Organic Program said they were concerned about the feasibility of mandatory testing, since "current rapid tests for GM organisms only detect the presence of GM material and not its level," the audit said.

However, the USDA has agreed to analyze "detection methods and protocols" to find whether transgenic contamination was intentional or inadvertent, said Robert Keeney, acting administrator of the agency's Agricultural Marketing Service, in a response letter.

The USDA should start by requiring farmers who use biotechnology to abide by practices that prevent the spread of transgenic material, said Lisa Bunin, organic policy director for the Center for Food Safety.

The group has opposed deregulation of transgenic crops like glyphosate-resistant alfalfa.

"Why should the burden be entirely on organic producers?" she said. "The USDA needs to show its commitment to prevent contamination. The time has come for the government to step in."

Organic farmers already take measures to protect themselves from transgenic material, said Bunin. "There's not enough shared responsibility on the part of users of GE technology."

It's heartening that auditors at the USDA's Office of Inspector General have decided to examine the issue, said Mark Kastel, co-founder of the Cornucopia Institute, which examines adherence to organic standards.

The propensity for cross-pollination with biotech alfalfa -- which was fully deregulated by USDA last year -- is still unknown, Kastel said.

Up until now, though, transgenic contamination of organic corn and soybeans has not been significant, he said.

"Based on our experience, there is no widespread problem," Kastel said. "They're not identifying a problem, they're identifying a vulnerability." - Capital Press